Alpha-synuclein (alphaSN) brain pathology is a conspicuous feature of several neurodegenerative diseases, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), the Lewy body variant of Alzheimer's disease (LBVAD), multiple systems atrophy (MSA), and neurodegeneration with brain iron accumulation type-1 (NBIA-1). Common to all of these diseases, termed synucleinopathies, are proteinaceous insoluble inclusions in the neurons and the glia which are composed primarily of alphaSN.
Lewy bodies and Lewy neurites are intraneuronal inclusions which are composed primarily of alphaSN. Lewy bodies and Lewy neurites are the neuropathological hallmarks Parkinson's disease (PD). PD and other synucleinopathic diseases have been collectively referred to as Lewy body disease (LBD). LBD is characterized by degeneration of the dopaminergic system, motor alterations, cognitive impairment, and formation of Lewy bodies (LBs). (McKeith et al., Clinical and pathological diagnosis of dementia with Lewy bodies (DLB): Report of the CDLB International Workshop, Neurology (1996) 47:1113-24). Other LBDs include diffuse Lewy body disease (DLBD), Lewy body variant of Alzheimer's disease (LBVAD), combined PD and Alzheimer's disease (AD), and multiple systems atrophy.
Disorders with LBs continue to be a common cause for movement disorders and cognitive deterioration in the aging population (Galasko et al., Clinical-neuropathological correlations in Alzheimer's disease and related dementias. Arch. Neurol. (1994) 51:888-95). Although their incidence continues to increase creating a serious public health problem, to date these disorders are neither curable nor preventable and understanding the causes and pathogenesis of PD is critical towards developing new treatments (Tanner et al., Epidemiology of Parkinson's disease and akinetic syndromes, Curr. Opin. Neurol. (2000) 13:427-30). The cause for PD is controversial and multiple factors have been proposed to play a role, including various neurotoxins and genetic susceptibility factors.
In recent years, new hope for understanding the pathogenesis of PD has emerged. Specifically, several studies have shown that the synaptic protein alpha-SN plays a central role in PD pathogenesis since: (1) this protein accumulates in LBs (Spillantini et al., Nature (1997) 388:839-40; Takeda et al., AM. J. Pathol. (1998) 152:367-72; Wakabayashi et al., Neurosci. Lett. (1997) 239:45-8), (2) mutations in the alpha-SN gene co-segregate with rare familial forms of parkinsonism (Kruger et al., Nature Gen. (1998) 18:106-8; Polymeropoulos MH, et al., Science (1997) 276:2045-7) and, (3) its overexpression in transgenic mice (Masliah et al., Science (2000) 287.1265-9) and Drosophila (Feany et al., Nature (2000) 404:394-8) mimics several pathological aspects of PD. Thus, the fact that accumulation of alpha-SN in the brain is associated with similar morphological and neurological alterations in species as diverse as humans, mice, and flies suggests that this molecule contributes to the development of PD.
An alpha-SN fragment, previously determined to be a constituent of AD amyloid plaques, was termed the non-amyloid-beta (non-Aβ) component of AD amyloid (NAC) (Iwai A., Biochim. Biophys. Acta (2000) 1502:95-109); Masliah et al., AM. J. Pathol (1996) 148:201-10; Ueda et al., Proc. Natl. Acad. Sci. USA (1993) 90:11282-6). Although the precise function of NAC is not known, it may play a critical role in synaptic events, such as neural plasticity during development, and learning and degeneration of nerve terminals under pathological conditions in LBD, AD, and other disorders (Hasimoto et al., Alpha-Synuclein in Lewy body disease and Alzheimer's disease, Brain Pathol (1999) 9:707-20; Masliah, et al., (2000).
AD, PD, and dementia with Lewy bodies (DLB) are the most commonly found neurodegenerative disorders in the elderly. Although their incidence continues to increase, creating a serious public health problem, to date these disorders are neither curable nor preventable. Recent epidemiological studies have demonstrated a close clinical relationship between AD and PD, as about 30% of Alzheimer's patients also have PD. Compared to the rest of the aging population, patients with AD are thus more likely to develop concomitant PD. Furthermore, PD patients that become demented usually have developed classical AD. Although each neurodegenerative disease appears to have a predilection for specific brain regions and cell populations, resulting in distinct pathological features, PD, AD, DLB and LBD also share common pathological hallmarks. Patients with familial AD, Down syndrome, or sporadic AD develop LBs on the amygdala, which are the classical neuropathological hallmarks of PD. Additionally, each disease is associated with the degeneration of neurons, interneuronal synaptic connections and eventually cell death, the depletion of neurotransmitters, and abnormal accumulation of misfolded proteins, the precursors of which participate in normal central nervous system function. Biochemical studies have confirmed the link between AD, PD and DLB.
The neuritic plaques that are the classic pathological hallmark of AD contain beta-amyloid (Aβ) peptide and non-beta amyloid component (NAC) peptide. Aβ is derived from a larger precursor protein termed amyloid precursor protein (APP). NAC is derived from a larger precursor protein termed the non-beta amyloid component of APP, now more commonly referred to as alpha-SN. NAC comprises amino acid residues 60-87 or 61-95 of alpha-SN. Both Aβ and NAC were first identified in amyloid plaques as proteolytic fragments of their respective full-length proteins, for which the full-length cDNAs were identified and cloned.
Alpha-SN is part of a large family of proteins including beta- and gamma-synuclein and synoretin. Alpha-SN is expressed in the normal state associated with synapses and is believed to play a role in neural plasticity, learning and memory. Mutations in human (h) alpha-SN that enhance the aggregation of alpha-SN have been identified (Ala30Pro and Ala53Thr) and are associated with rare forms of autosomal dominant forms of PD. The mechanism by which these mutations increase the propensity of alpha-SN to aggregate are unknown.
Despite the fact that a number of mutations can be found in APP and alpha-SN in the population, most cases of AD and PD are sporadic. The most frequent sporadic forms of these diseases are associated with an abnormal accumulation of Aβ and alpha-SN, respectively. However, the reasons for over accumulation of these proteins is unknown. Aβ is secreted from neurons and accumulates in extracellular amyloid plaques. Additionally Aβ can be detected inside neurons. Alpha-SN accumulates in intraneuronal inclusions called LBs. Although the two proteins are typically found together in extracellular neuritic AD plaques, they are also occasionally found together in intracellular inclusions.
The mechanisms by which alpha-SN accumulation leads to neurodegeneration and the characteristics symptoms of PD are unclear. However, identifying the role of factors promoting and/or blocking alpha-SN aggregation is critical for the understanding of LBD pathogenesis and development of novel treatments for its associated disorders. Research for identifying treatments has been directed toward searching for compounds that reduce alpha-SN aggregation (Hashimoto, et al.) or testing growth factors that will promote the regeneration and/or survival of dopaminergic neurons, which are the cells primarily affected (Djaldetti et al., New therapies for Parkinson's disease, J. Neurol (2001) 248:357-62; Kirik et al., Long-term rAAV-mediated gene transfer of GDNF in the rat Parkinson's model: intrastriatalo but not intranigral transduction promotes functional regeneration in the lesioned nigrostriatal system, J. Neurosci (2000) 20:4686-4700). Recent studies in a transgenic mouse model of AD have shown that antibodies against Aβ 1-42 facilitate and stimulate the removal of amyloid from the brain, improve AD-like pathology and resulting in improve cognitive performance (Schenk et al., Immunization with amyloid-β attenuates Alzheimer-disease-like pathology in PDAPP mouse, Nature (1999) 408:173-177; Morgan et al., A-beta peptide vaccination prevents memory loss in an animal model of Alzheimer's disease, Nature (2000) 408:982-985; Janus et al., A-beta peptide immunization reduces behavioral impairment and plaques in a model of Alzheimer's disease, Nature (2000) 408:979-82). In contrast to the extracellular amyloid plaques found in the brains of Alzheimer's patients, Lewy bodies are intracellular, and antibodies do not typically enter the cell.
Surprisingly, given the intracellular nature of LBs in brain tissue, the inventors have succeeded in reducing the number of inclusions in transgenic mice immunized with synuclein. The present invention is directed inter alia to treatment of PD and other diseases associated with LBs by administration of synuclein, fragments of synuclein, antigens that mimic synuclein or fragments thereof, or antibodies to certain epitopes of synuclein to a patient under conditions that generate a beneficial immune response in the patient. The inventors have also surprisingly succeeded in reducing the number of inclusions in transgenic mice immunized with Aβ. The present invention is directed inter alia to treatment of PD and other diseases associated with LBs by administration of Aβ, fragments of Aβ, antigens that mimic Aβ or fragments thereof, or antibodies to certain epitopes of Aβ to a patient under conditions that generate a beneficial immune response in the patient. The invention thus fulfills a longstanding need for therapeutic regimes for preventing or ameliorating the neuropathology and, in some patients, the cognitive impairment associated with PD and other diseases associated with LBs.